The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 16, 2022
Filed:
Jul. 28, 2020
Analog Devices International Unlimited Company, Limerick, IE;
Andrew J. Gardner, Santa Barbara, CA (US);
Analog Devices International Unlimited Company, Limerick, IE;
Abstract
A PoDL system that uses a center-tapped transformer, for galvanic isolation of the PHY, has AC-coupling capacitors in series between the transmission wires and the transformer's secondary windings for blocking DC voltages generated by a PSE power supply. The center tap is conventionally connected to ground. As a result, one capacitor sees the full VPSE voltage across it, and the other capacitor sees approximately 0 V across it. Since the effective value of a ceramic capacitor significantly reduces with increasing DC bias voltages across it, the effective values of the capacitors will be very different, resulting in unbalanced data paths. This can lead to conversion of common mode noise and corrupt the data. To avoid this, a resistor divider is used to generate VPSE/2, and this voltage is applied to the center tap of the transformer. Therefore, the DC voltage across each capacitor is approximately VPSE/2, so their values remain equal.